Preparation of star polymers

ABSTRACT

Divinyl benzene and/or diisopropenyl benzene in hydrocarbon solvent is added over a period of time at low temperature to a hydrocarbon solvent containing a C 2-20  normal, secondary or tertiary alkyl or cycloalkyl lithium compound and a tertiary alkylamine having 2-4 carbon atoms prepared at low temperature to provide an initiator having an average of from 4 to 9 C-Li sites and a VPO Mn of from about 750 to 4,000. These initiators are useful in polymerizing dienes and vinyl monomers to provide star polymers having an average of from about 4 to 9 arms or branches. These star polymers among other things are useful low profile or low shrink additives of FRPs, e.g., glass fiber reinforced plastics.

This invention relates to the preparation of Li initiators having anaverage of from about 4 to 9 carbon-lithium sites in the molecule anduseful in the anionic solution polymerization of ethylenicallyunsaturated monomers like butadiene and styrene.

OBJECTS

An object of this invention is to provide a lithium initiator having anaverage of from about 4 to 9 carbon-lithium sites and a method formaking the same.

Another object is to provide radial or star polymers having an averageof from about 4 to 9 arms and a method for making the same.

Still another object is to provide thermosetting vinyl ester resin andpolyester resin glass fiber molding compositions containing radial orstar polymers having an average of from about 4 to 9 arms as low shrinkadditives.

These and other objects and advantages of the present invention willbecome more apparent to those skilled in the art from the followingdetailed description and examples.

SUMMARY OF THE INVENTION

According to the present invention low molecular weight tertiary aminesare mixed with alkyl and cycloalkyl lithium compounds in hydrocarbonsolvent at low temperature after which there is very slowly added at lowtemperatures with stirring to avoid substantial polymerization adiethylenically unsaturated benzene compound to provide a lithiuminitiator having an average of from about 4 to 9 carbon-lithium sitesand a VPO Mn of about 750 to 4,000. These initiators can then be used inanionic solution polymerization to polymerize ethylenically unsaturatedmonomers to provide radial or star polymers having an average of fromabout 4 to 9 arms or branches and having Li atoms on the ends of thearms or branches. If desired the Li atoms on the ends of the arms of thepolymers can then be reacted with epoxides or CO₂ and then protonated orhydrolyzed to provide star polymers with OH or COOH groups on the endsof the arms and which are available for further reaction.

DISCUSSION OF DETAILS AND PREFERRED EMBODIMENTS

The initiator is prepared by adding the tertiary amine to the solutionof the organolithium compound in a hydrocarbon solvent under an inertatmosphere. During addition, the mixture should be stirred and thetemperature should be sufficiently low to avoid thermal decomposition ofthe organolithium compound. Desirably the temperature should bemaintained at from about 0° to 25° C., preferably at from about 0° to10° C. The molar ratio of the tertiary amine to the organolithiumcompound should be about 4 to 1. Next, to the solution of the tertiaryamine and organolithium compound there is added under an inertatmosphere, very slowly, preferably dropwise, over an extended period oftime with stirring, a solution in hydrocarbon solvent of thediethylenically unsaturated benzene compound in the same temperatureranges as noted above. The molar ratio of the organolithium compound tothe diethylenically unsaturated benzene compound is about 6 to 5 or aratio of 1:0.83. The moles of the diethylenically unsaturated benzenecompound are based on the pure or essentially pure diethylenicallyunsaturated benzene compound and do not include any other materialspresent (such as in the case of divinyl benzene: ethyl vinyl benzene,diethyl benzene and so forth). These conditions for preparation of theinitiator should be maintained to prevent formation of gel or to preventpolymerization and to obtain a hydrocarbon soluble initiator with anaverage of from about 4 to 9 carbon-lithium sites and a VPO Mn of fromabout 750 to 4,000 for use in anionic polymerization.

The organolithium compound used in the present invention has the generalformula RLi where R represents a normal, secondary or tertiary alkyl orcycloalkyl radical having from 2 to 20 carbon atoms. Examples of theorganolithium compounds are ethyllithium, n-propyllithium,isopropyllithium, n-butyllithium, isobutyllithium, sec-butyllithium,tert-butyllithium, n-amyllithium, isoamyllithium, n-hexyllithium,2-ethylhexyllithium, n-octyllithium, n-decyllithium, cyclopentyllithium,cyclohexyllithium, methylcyclohexyllithium, cyclohexylethyllithium andthe like and mixtures thereof. Preferably, R is an alkyl radical of from2 to 10 carbon atoms, particularly sec-butyllithium.

The tertiary amine used in the preparation of the initiator should be atertiary alkyl amine having from 2 to 4 carbon atoms in the alkyl groupand should be liquid in the temperature range of from about 0° to 25° C.Examples of such amines are triethylamine, triisobutylamine,tripropylamine and the like and mixtures thereof. Of these amines, it ispreferred to use triethylamine.

The diethylenically unsaturated benzene compound used can be 1,2-divinylbenzene, 1,3-divinyl benzene or 1,4-divinyl benzene or mixture thereof.The divinyl benzenes as obtained commercially generally contain fromabout 25 to 95% of the divinylbenzene or mixed isomers of divinylbenzene with the balance being substantially ethyl vinyl benzenes. Verysmall amounts of diethyl benzene, naphthalene and azulene, also, may bepresent with the divinyl benzene(s). Diisopropenylbenzene, also, can beused such as 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene and1,4-diisopropenylbenzene and mixtures thereof. Mixtures of divinylbenzene(s) and diisopropenylbenzene(s) may be used. It is preferred touse divinylbenzene(s). Any monomeric compound present like ethylvinylbenzene enters into the initiator as part of the chain but does not leadto increased carbon-lithium functionality. Likewise, any non-reactivematerials such as azulene and naphthalene possibly present in smallquantities in the divinylbenzene merely act as diluents or solvents andcan be stripped from the final polymer along with the removal of thepolymerization solvent.

The solvent used for the preparation of the initiator should be asolvent for the organo lithium compound, tertiary amine and benzenecompound so that a solution of the initiator may be obtained. Likewise,the solvent used for polymerization should be a solvent for theinitiator, monomer and polymer obtained. Examples of solvents which maybe used to obtain preferred high 1,4 polydiene microstructure arehydrocarbons like hexane, heptane, octane, isooctane, cyclohexane,cycloheptane, benzene, toluene, the xylenes and so forth. Mixtures ofsolvents may be used where they are compatible. The solvent preferablyshould not have a very labile carbon-hydrogen bond and should not act atleast substantially as a chain transfer agent. The solvents should beliquids at temperatures of from about 0° to 120° C.

The inert atmosphere used in the preparation of the initiator and usedduring polymerization can be nitrogen, argon, helium, neon and so forth.

The ethylenically unsaturated polymerizable monomers to be polymerizedusing the initiators of the present invention are those having anactivated unsaturated double bond, for example, those monomers whereadjacent to the double bond there is a group more electrophilic thanhydrogen and which is not easily removed by a strong base. Examples ofsuch monomers are nitriles like acrylonitrile and methacrylonitrile;acrylates and alkacrylates like methyl acrylate, ethyl acrylate, butylacrylate, ethyl hexyl acrylate, octyl acrylate, methyl methacrylate,ethyl methacrylate, butyl methacrylate, methyl ethacrylate, ethylethacrylate, butyl ethacrylate and octyl ethacrylate; the dienes such asbutadiene-1,3, 2,3-dimethyl butadiene, piperylene and isoprene; and thevinyl benzenes like styrene, alpha methyl styrene, p-tertiary butylstyrene, divinyl benzene, methyl vinyl toluene and para vinyl tolueneand the like and mixtures of the same. Preferred monomers to use arebutadiene and mixtures of butadiene and styrene.

Depending on the monomer employed, the resulting star polymers can berubbery, resinous, or thermoplastic. They, also, can be homopolymers,pure block copolymers or graded block copolymers. Random copolymers maybe obtained by carefully adding (programming) monomer additions to thereactor. Alternatively, small amounts of randomizing agents liketetrahydrofuran may be used during polymerization. These star polymersas produced usually do not contain gel and have an average of from about4 to 9 arms.

The obtained number-average molecular weight of the star polymer in theabsence of chain transfer is controlled by the molecular weightcalculated from the ratio of grams of monomer polymerized to moles ofinitiator charged. Conversions of monomer to polymer up to about 100%are obtained.

Temperatures during solution polymerization can vary from about 0° to120° C. Preferably, polymerization temperatures are from about 20° to80° C. Times for polymerization will be dependent on the temperature,amount of initiator, type of polymers desired and so forth. Only minoramounts of the initiator are necessary to effect polymerization.However, the amount of initiator employed may vary with the type ofpolymer desired. For example, in general, when making polymers having ahigh number average molecular weight using a given amount of monomer,only a small amount of the initiator is necessary whereas when making alow number average molecular weight polymer, larger amounts of theinitiator are employed. Moreover, since the polymer is a living polymer,it will continue to grow as long as monomer is fed to the polymerizationsystem. Thus, the molecular weight can be as high as several hundredthousand or even more. On the other hand, very high molecular weightpolymers require lengthy polymerization times for a given amount of theinitiator, and at lower initiator concentrations the polymerization ratemay drop. A useful range of initiator to obtain readily processablepolymers in practicable times is from about 0.00001 to 0.10, preferablyfrom about 0.00033 to 0.005, mol of the initiator per 100 grams total ofmonomer(s).

The polymerization is conducted in a liquid hydrocarbon solvent. Whilebulk polymerization may be used, such presents heat transfer problemswhich should be avoided. In solvent polymerizations it is preferred tooperate on a basis of not over about 15 to 20% polymer solidsconcentration in the solvent to enable ready heat transfer andprocessing.

Polymerization, of course, should be conducted in a closed reactor, suchas a glass polymerization bottle, glass reaction flask or, preferably, apressure reactor, fitted with a stirrer, heating and cooling means, withmeans to flush with or pump in an inert gas and so forth in order topolymerize under inert or non-reactive conditions, with means to chargemonomer, solvent and initiator, venting means and with means to recoverthe resulting polymer and so forth. Small amounts of the initiator or ofbutyl lithium or other alkyl or cycloalkyl lithium compound may be addedto the monomers and/or solvents prior to use as a scavenger to removetraces of water or other impurities which might adversely affect thepolymerization. Alternatively or additionally, the monomers and/orsolvents may be subject to reduced pressure or other treating agents tofree them of water and other chain terminating agents.

The polyfunctional lithium initiator of this invention, also, may beused with the barium di(tert-alkoxide-hydroxide) salts of U.S. Pat. Nos.3,992,561 and 4,260,712 and the barium salts of U.S. Pat. No. 3,692,213.

Since the star polymer in solution in the polymerization media is aliving polymer or since the polymerization is a non-terminatingpolymerization (unless positively terminated by failure to add monomeror by adding a terminating agent such as methanol) and since the livingpolymer contains terminal lithium atoms, it can be treated with anepoxide like ethylene oxide or with CO₂ and then protonated orhydrolyzed to provide a polymer with terminal hydroxyl groups orcarboxyl groups, respectively.

Polymerization may be terminated by adding water, alcohol or other agentto the polymeric solution. After the star polymer has been recoveredfrom the solvent media and dried, a suitable antioxidant such as2,6-di-tert-butyl-p-cresol or other antioxidant may be added to thesame. However, the antioxidant may be added to the polymeric solutionbefore it is stripped of solvent.

The star polymers produced by the method of the present invention can becompounded and cured in the same manner as other plastic and rubberypolymers. For example, they can be mixed with sulfur or sulfurfurnishing materials, peroxides, carbon black, SiO₂, TiO₂, Sb₂ O₃, rediron oxide, other rubber fillers and pigments, tetramethyl or ethylthiuram disulfide, benzothiazyl disulfide and rubber extending orprocessing mineral or petroleum oils and the like. Stabilizers,antioxidants, UV light absorbers and other antidegradants can be addedto these polymers. They can also be blended with other polymers likenatural rubber, butyl rubber, butadiene-styrene-acrylonitrileterpolymers, polychloroprene, SBR, polyurethane elastomers, polystyreneand so forth.

The star polymers produced by the method of the present invention can beused in making protective coatings for fabrics, films, gaskets, belts,hose, shoe soles and electric wire and cable insulation, and may be usedas plasticizers and polymeric fillers for other plastics and rubbers.With large amounts of sulfur hard rubber products can be made.

The star polymers produced by the method of the present invention aspointed out above have an average of from about 4 to 9 arms with eacharm containing a terminal Li atom. The polymer can then be protonatedwith an alcohol like methanol which forms LiOR and results in terminal##STR1## groups on the end of the arms. Alternatively, the Li containingpolymer may be treated with ethylene oxide or propylene oxide and thenprotonated to provide the arms with hydroxyl end groups which then maybe reacted with polyisocyanates such as tolylene diisocyanate ordiphenylmethane-4,4'-diisocyanate to form polyurethanes. Also, the Licontaining polymer may be reacted with CO₂ and then may be hydrolyzed toform COOH groups on the ends of the arms which then may be reacted withglycols to form polyesters. They, also, are useful in Fiber ReinforcedPlastics (FRPs).

If desired these star polymers containing a Li atom on the end of eacharm may be coupled with such coupling agents as silicon tetrachloride,1,2-dichloroethane and so forth to form networks.

In particular, rubbery star copolymers prepared according to theteaching of the present invention having on the average of from about 4to 9 arms and a number average molecular weight of from about 50,000 to250,000 and comprising from about 10 to 40% by weight of styrene andfrom 90 to 60% by weight of butadiene-1,3 and which can be pure block,graded block or random copolymers, preferably pure block copolymers withstyrene blocks on the ends of the arms, are useful as low profile or lowshrink additives for FRPs, glass fiber reinforced plastics such asthermosetting polyester resin or vinyl ester resin glass fibercompositions. The amount by weight of the star polymer in the FRP isfrom about 5 to 15% by weight based on the total weight of the organicconstituents in the FRP. An advantage of using the star polymer of thisinvention in the polyester or vinyl ester resin composition is that ithas less tendency to increase the viscosity of the composition ascompared to a linear or substantially linear polymer of about the sameMW and chemical type.

The glass fiber reinforced thermoset plastic (FRP) can be a sheetmolding compound (SMC) or a bulk molding compound (BMC), or otherthermosetting FRP material as well as a high strength molding compound(HMC) or a thick molding compound. The FRP substrate can have from about10 to 75% by weight of glass fibers. The SMC compound usually containsfrom about 25 to 30% by weight of glass fibers while the HMC compoundmay contain from about 55 to 60% by weight of glass fibers. The glassfiber reinforced thermoset plastic (FRP) substrate can be rigid orsemirigid (may contain a flexibilizing moiety such as an adipate groupin the polyester).

The thermosetting composition or composition which is added to or mixedwith the glass fibers, also, can contain fillers, maturation agents,inhibitors, mold release agents, catalysts, antioxidants, plasticizers,crosslinking monomers, pigments, and so forth such calcium carbonate,magnesium hydroxide, calcium hydroxide, magnesium oxide, zinc stearate,peroxide catalysts, benzoquinone, styrene, methylmethacrylate and soforth. Unsaturated polyesters useful in glass fiber thermosets are knownas shown by "Modern Plastics Encyclopedia," 1975-1976, October, 1975,Vol. 52, No. 10A, McGraw-Hill, Inc., New York, pages 61, 62 and 105 to107; "Modern Plastics Encyclopedia," 1979-1980, October, 1979, Volume56, Number 10A, pages 55, 56, 58, 147 and 148, McGraw-Hill, Inc., NewYork, N.Y., and "Modern Plastics Encyclopedia," 1980-81, October, 1980,Volume 57, Number 10A, pages 59, 60, and 151 to 153, McGraw-Hill, Inc.,New York, N.Y. Vinyl ester resins are known, for example, see "HeatResistant Vinyl Ester Resins," Launikitis, Technical Bulletin SC:116-76,Shell Chemical Company, June, 1976; Shell Chemical Company TechnicalBulletin SC:16-76 and U.S. Pat. No. 3,876,726 and elsewhere. These FRPcompositions can be used in the manufacture of automobile parts such asgrille and headlamp assemblies, deck hoods, fenders, door panels androofs as well as in the manufacture of food trays, appliance andelectrical components, furniture, machine covers and guards, bathroomcomponents, structural panels and the like. The FRP parts or moldingsfurther can be in-mold coated according to the teachings of U.S. Pat.Nos. 4,081,578; 4,189,517; 4,222,929 and 4,245,006.

The following examples will serve to illustrate the present inventionwith more particularity to those skilled in the art. In these examples,parts are part by weight unless otherwise noted.

EXAMPLE 1 Preparation of Soluble Polyfunctional Initiator at 8° C.

42.8 grams of secondary-butyllithium (s-BuLi) in solution in cyclohexanewere charged by syringe to a pre-weighed, dry, argon-purged pint bottleto give 82.39 mmoles s-BuLi. This s-BuLi was purchased as a solution incyclohexane from Foote Mineral Company and analyzed for carbon-lithiumconcentration prior to use. The solution was cooled with stirring to +5°C. in an ice-water bath, and 34.0 grams (0.336 mole) of triethylaminewere added by syringe over a 30-minute time span. An exotherm wasnoticed, but the temperature was held between +5° to +10° C. by thetriethylamine addition rate. The yellow s-BuLi solution darkened toorange with triethylamine addition. The molar ratio of TEA/s-BuLi was4.08. 68.73 mls of divinylbenzene (DVB) (contained 68.66 mmoles or 8.95g of DVB) solution in benzene (Foster Grant Company#) were addeddropwise to the rapidly stirred s-BuLi/TEA solution over a six-hour timespan under argon. The divinyl benzene amount is figured as divinylbenzene and does not include any ethyl vinyl benzene etc. Upon additionof the first few drops of DVB solution, a bright red color was seen. Thecolor deepened throughout addition to a very deep red. The rate ofaddition was slowed for the last 20% of DVB solution. No evidence ofinsolubility was observed. The reaction mixture was held below +8° C.through the DVB addition. The total amount of DVB added was 68.66 mmolesto give a mole ratio of 6 s-BuLi/5 DVB. After the DVB addition wascomplete, the solution was allowed to slowly warm with stirringovernight. No change in appearance was seen, with the solution remaininghomogeneous with no evidence of insolubles.

The addition product of divinylbenzene (and of ethylvinylbenzene, ifpresent) and secondary-butyllithium is referred to as the adduct orinitiator. When the solution is used, it is called the adduct orinitiator solution.

#Foster Grant Company, Inc.--general sample--The DVB was vacuumdistilled at 47°-49° C. and 0.8 mm pressure from dibutylmagnesium andthe main cut divided. A small amount of the distillate was retained foranalysis. The rest was diluted with dry benzene. Gas chromatography/Massspectrometry (GC/MS) analysis assuming equal response gave the followingresults: 56.6% DVB (all isomers), 42.4% EVB, 0.7% naphthalene orazulene, 0.2% diethylbenzene and 0.1% hydrocarbons (hexane, cyclohexane)introduced with the dibutylmagnesium.

A. Gel Permeation Chromatography (GPC) Analysis

1.2 grams of the adduct solution were added to 20 ml benzene (GPC) andaddition of a drop of methanol caused the color to fade to pale yellow.No further color change was seen with the addition of a second drop ofmethanol. Two milliliters of this solution was injected into a WatersAssociate GPC 200 equipped with the following columns: 2,000-5,000 A,3×10³ A, 400 A and 250 A. This column was assembled to give highresolution in the low molecular weight region. The sample was run inbenzene at 45° C. It showed a broad polymodal molecular weightdistribution.

B. Vapor Phase Osmometry (VPO)

20 ml of adduct solution were terminated by addition of methanol slowlyto give a pale yellow solution (protonation). After dilution with 20 mlbenzene, the hydrocarbon solution was extracted with dilute HCl followedby extraction with distilled water until the aqueous phase was neutral.The organic phase was passed through anhydrous MgSO₄ several times togive a clear yellow solution. The MgSO₄ was washed each time withbenzene to avoid loss of protonated adduct. The recovered adductsolutions were combined, frozen, and the product collected afterfreeze-drying. The product was then vacuum-dried at +45° C. maximum. Ayellow, tacky material was obtained. The number average molecular weightMn.sub.(vpo) of this material was determined in benzene using a HitachiPerkin-Elmer 115 Molecular Weight Apparatus. Benzil was used tocalibrate the instrument. The Mn.sub.(vpo) found was 1450. This was ingood agreement with the theoretical Mn of 1571, based on completereaction of s-BuLi with the vinyl groups of both divinylbenzene andethylvinylbenzene present in the system.

C. Carbon-Lithium Determination

A sample of the adduct solution was withdrawn and terminated withhydroxyl tritiated n-propanol. The tritiated adduct was isolated, dried,total solids determined, and prepared for scintillation measurements.Tritium content was determined on a Packard #527 Liquid ScintillationSpectrometer. The activity of the tritiated n-propanol was determinedthe same day as reference. The carbon-lithium found was 3.447mmoles/gram solids at a total solids of 14.8%. The theoreticalcarbonlithium content was 4.05 mmoles/gram at 14.8% total solids.

D. Nuclear Magnetic Resonance

A portion of the protonated adduct (0.2 gram) from B, above, wasdissolved in 2.0 grams deuterated benzene. Proton NMR spectra wereobtained at 40° C. using a Varian A60-A NMR Spectrometer withtetramethylsilane as a reference. The ratio of s-Bu/DVB was found to be0.95 versus 1.09 expected from carbonlithium retention. No residualunsaturation was seen. The charge ratio was 6/5 or 1.2. The differenceor C-Li loss is probably due to impurities.

E. Gas Chromatography

Gas chromatography was used to examine the polyfunctional initiator anda control of s-BuLi before and after termination. Samples of the vaporphase revealed that no butane increase was observed for thepolyfunctional initiator upon protonation, indicating no residuals-BuLi. A large increase was seen with the s-BuLi control as expected.This shows all of the sec-BuLi was consumed in the initiator formation.

F. Determination of Average Functionality

The average functionality of the initiator or adduct was calculated fromthe number average molecular weight of the protonated initiator by vaporphase osmometry, and the equivalent weight (Me) per C-Li group obtainedby tritiation according to:

Found Functionality=Mn(vpo)/Me(C-Li)=grams per mole/grams perC-Li=C-Li/Mole (Eq. 1)

The average functionality of this initiator was 5.04 carbonlithiums permole (or molecule of initiator).

G. Aging Studies

Carbon-lithium analysis by tritiation was run just after the adductpreparation and three and one-half months later. In the interim, theinitiator (adduct) was stored under argon pressure in a refrigerator(+5° C.), except when being sampled for polymerization reactions. Overthe 31/2 months, the active carbon-lithium content decreased from 3.48meq C-Li/gram of solids to 3.38 meq C-Li/gram of solids, a decrease ofonly 2.8%. Room temperature aging studies were undertaken. A portion ofthe initiator was transferred to a clean, dry bottle and carbon-lithiumcontent determined periodically over a two-week time span. Betweensampling, the initiator was stored at room temperature under an inertatmosphere. After 14 days, a continuous loss of active carbon-lithiumfrom 3.38 meq C-Li/gram of solids to 3.13 meq C-Li/gram of solids wasseen. This represents a 7.4% decrease in activity. It should be notedthat some loss of C-Li activity is potentially possible due toadventitious termination during the multiple samplings of a relativelysmall portion of initiator.

These results confirm the preparation of a polyfunctional initiatorwhich is relatively stable when stored at 5° C.

EXAMPLE 2

Attempted Preparation of a Polyfunctional Initiator in the Absence ofTriethylamine

This was an attempt to form an adduct (6 s-BuLi/5 DVB) in the absence oftriethylamine, and emphasizes the need for the amine solubilizing agent.30 mls of a 1.288 meq/ml solution of sec-BuLi in cyclohexane to give38.64 meq sec-BuLi were charged by syringe to a pre-weighed,argon-purged pint bottle. The solution was cooled to +7° C. using anice-water bath. 29.35 mls of a DVB solution in benzene were addeddropwise over the course of three hours under argon. Suddenly, after thethree hours, with the addition of several more drops, the bright, redreaction solution formed a gel-like mass. At this point, the mole ratioof s-BuLi/DVB was 1.65. No further addition of DVB solution was made.Triethylamine was added to the solution (4 TEA/1 s-BuLi) and somebreak-up of the gel-like consistency occurred along with a deepening ofcolor intensity. Over the next two hours, chunks of gel-like materialwere still in evidence. No characterization was obtained due toinsolubility.

EXAMPLE 3 Preparation of a Polyfunctional Initiator at 22° C. in thePresence of Triethylamine

32.0 grams of s-BuLi solution in cyclohexane were charged by syringe toa pre-weighed, dry, argon-purged pint bottle to give 62.24 mmoless-BuLi, which had been purchased from Foote Mineral Company and analyzedfor carbon-lithium content prior to use. The solution was cooled in anice-water bath and 25.8 grams of triethylamine were added over 30minutes with stirring. The molar ratio of TEA/s-BuLi was 4.1. Theorange-yellow solution was warmed to +22° C. 139.1 mls of divinylbenzenesolution in benzene (Dow Chemical Company DVB##) were added dropwiseunder argon to the stirred s-BuLi/TEA solution over six hours. The moleratio of s-BuLi/DVB was about 6/5. A deep red, clear solution was inevidence. The solution was allowed to remain at room temperatureovernight. No apparent change was seen.

##Dow Chemical Company--general samples--The DVB was vacuum distilledfrom CaH₂ and was subsequently diluted with dry benzene. GC/MS analysisassuming equal response gave the following results: 52.4% DVB (allisomers), 45.3% EVB, 1.8% diethylbenzene and 0.5% naphthalene.

Adduct Characterization

The procedures described in detail in Example 1 were followed. The GPCcurve revealed a buildup of high molecular weight material. The averagefunctionality of this adduct (calculated from equation 1) was 8.81. ItsVPO Mn was 2908.

EXAMPLE 4 Preparation of a Polyfunctional Initiator at 7° C. in thePresence of Triethylamine

19.4 grams of s-BuLi solution in cyclohexane were charged by syringe toa pre-weighed, dry, argon-purged pint bottle to give 37.33 mmoles s-BuLiwhich had been purchased from Foote Mineral Company and analyzed forcarbon-lithium content prior to use. The solution was cooled using anice-water bath and 15.41 grams of triethylamine were added over a30-minute time span with stirring. The maximum temperature of thesolution was +8° C. The molar ratio of TEA/s-BuLi was 4.08. 83.4 mlsdivinylbenzene solution in benzene (Dow Chemical Company DVB) were addedunder argon dropwise to the rapidly stirred s-BuLi/TEA solution over sixhours. The maximum temperature during the DVB addition was +7° C. Themole ratio of s-BuLi/DVB was about 6/5. The deep red, clear solution waspacked in ice but was allowed to warm overnight. In the morning, nochange was observed.

Adduct Characterization

The procedures described in detail in Example 1 were followed. The GPCcurve shows less high molecular weight buildup than for Example 3 whichwas prepared at +22° C. The average functionality of this adduct(calculated from equation 1) was 6.3. Its VPO Mn was 2000.

EXAMPLE 5 Preparation of Omega-Reactive Radial Polymers, Preparation ofHydroxyl-terminated Polybutadiene

1.5 grams (0.306 mmole CLi) of divinylbenzene/secbutyllithium adduct(initiator) solution (f=4.85) were added dropwise by syringe to asolution of 434.9 grams toluene (sieve-dried) and 45.2 grams (0.836mole) sieve-dried butadiene in a dry, argon-purged quart polymerizationbottle until a pale yellow color indicating active carbon-lithium wasproduced. The presence of active carbon-lithium was taken to indicatethe successful titration (scavenging) of impurities in the system. Afterthis, an additional 35.2 grams of adduct solution (7.18 mmoles CLi) wereadded to effect polymerization. The bottle contained a deep red, clearsolution. The polymerization was carried out overnight at 30° C. withmixing. A viscous, slightly turbid orange solution resulted. Theconversion was about 100%.

9.7 grams ethylene oxide solution in toluene were added by syringe togive 15.69 mmoles EO (2.19 EO/CLi). The contents were vigorously shakenand a highly associated gel-like mass was formed, accompanied by colorloss, locally throughout the solution. The presence of less viscouscolored areas indicated incomplete mixing. After several days at 30° C.,an apparently uniform gel-like mass was found. A small amount of moremobile fluid was present.

20 mls methanol were added, effecting an immediate loss of viscosity togive a clear, colorless, slightly viscous solution to form OH groups onthe end of the polymer and LiOCH₃. The polymer was precipitated inexcess methanol and analyzed, after isolation and vacuum drying, formicrostructure and hydroxyl content. The polybutadiene microstructurewas established by nuclear magnetic resonance (¹³ C NMR) to be 40.3%trans-1,4, 25.3% cis-1,4 and 34.4% vinyl for this low molecular weightpolymer. The hydroxyl content of this polymer was found to be 0.156 moleOH/gram polymer. This corresponds to an average of 4.7 hydroxyls permolecule. This value was established using the following formula,Equation 2: ##EQU1##

This OH containing polymer exhibited the following: Mn=40,000,Mw=60,000, H.I.=1.51 by GPC and Mn=33,000 by VPO.

11.78 grams of this OH containing star polymer were dissolved in 9.61grams of toluene and mixed with 5.61 grams of a solution of4,4'-diisocyanato diphenyl methane in toluene (1.2 NCO/OH) and 0.081gram stannous octoate catalyst (T-9). A film was cast on Teflon using a0.040-inch spacer bar. The system was cured under nitrogen at 65° C. fortwo hours to crosslink and chain extend the polymer and evaporate thesolvent and to give a pale yellow film. This film had an ultimatetensile strength of 0.714 megapascal at 400% elongation.

EXAMPLE 6 Preparation of a Linear Hydroxyl-terminated PolybutadieneControl

0.4 gram of dilithioisoprene (Lithium Corporation of America, f=2)solution (0.41 mmole CLi) in toluene containing a small amount oftriethyl amine was added dropwise by syringe to a solution of 463.2grams toluene and 76.0 grams butadiene in a dry, argon-purged quartpolymerization bottle to color end-point. The presence of color,indicating active carbon-lithium, signified tritration of impurities inthe system. Immediately, an additional 15.7 grams dilithioisopreneinitiator (16.1 mmoles CLi) solution were added for polymerization togive an orange, slightly turbid solution. The polymerization waseffected overnight at 30° C. to give a clear, yellow polymer solution.The conversion was about 100%.

19.3 grams ethylene oxide solution in toluene were added to give 31.23mmoles EO (1.94 EO/CLi). The contents were shaken and a gel-like masswas formed concurrent with fading of the color. After several days, auniform gel-like mass was obtained with only a small amount of moremobile fluid in evidence.

The addition of 20 mls methanol effected a marked loss in viscosity togive a fluid, colorless solution. The polymer was precipitated andanalyzed, after isolation and vacuum-drying, for hydroxyl content, whichwas found to be 0.184 mmole OH/gram polymer. This corresponds to anaverage of 1.73 hydroxyls per molecule according to equation 2, assumingthe functionality of the dilithioisoprene initiator equals 2. This OHcontaining polymer exhibited the following: Mn=17,000, Mw=22,000 andH.I.=1.32 by GPC and Mn=8,900 by VPO.

10.14 grams of this OH containing polymer dissolved in 10.31 grams oftoluene were mixed with 5.7 grams of a solution (1.2 NCO/OH) of4,4'-diisocyanato diphenyl methane in toluene and 0.078 gramstannous-octoate catalyst (T-9). A film was cast on Teflon using a0.040-inch spacer bar. The system was cured under nitrogen at 65° C. togive a pale yellow film. This film had an ultimate tensile strength of0.324 megapascal at 410% elongation.

This comparison shows the higher tensile strength of the starhydroxyl-terminated polybutadiene over its linear counterpart inisocyanate extensions.

EXAMPLE 7 Preparation of Hydroxyl-terminated Polystyrene

Five drops (approximately 0.5 gram, 0.3 mmole CLi) ofdivinyl-benzene/sec-butyllithium adduct or initiator solution (f=4.815)were added dropwise by syringe to a solution of 76.7 grams styrene and568.0 grams sieve-dried toluene in a dry, argon-purged polymerizationbottle to a pale yellow color end-point indicating active carbon-lithiumand successful titration of impurities in the system. Immediately, 28.2grams of the adduct or initiator solution (17.22 mmoles CLi) were addedto effect polymerization. A deep red solution with some small gel-likeparticles was observed. When inspected after 21/2 hours at 25° C., thedeep red solution contained no evidence of insolubles. The bottle wasrotated at 25° C. overnight to reveal no obvious change in appearance inthe morning. The conversion was about 100%.

21.29 grams of ethylene oxide stock solution in sieve-dried toluene wereadded to give 34.44 mmoles ethylene oxide (2 EO/CLi). With vigorousshaking, a rapid buildup of highly associated gel-like particles of paleorange uniform color was observed. After rotation at 25° C. overnight,some color remained. After rotation at 50° C. overnight, a clear,colorless, highly associated mass was in evidence.

10 mls methanol were added and, with shaking, a loss of association togive a clear, colorless, slightly viscous solution occurred. The polymerwas precipitated in acidified methanol, redissolved in warm cyclohexaneand reprecipitated in methanol. The solvent was removed and the polymerredissolved in warm cyclohexane and subsequently freeze-dried. 79.5grams of polymer were recovered versus 81.7 grams theoretical (includingincorporated initiator). The hydroxyl content of this polymer was foundto be 0.136 mmole OH/gram polymer, which corresponds to an average of3.10 hydroxyls per molecule (Eq. 2). This OH containing polymerexhibited a Mn of 17,900 by VPO.

EXAMPLE 8 Preparation of Carboxyl-terminated Styrene-Butadiene-StyreneBlock Copolymer

0.23 gram of divinylbenzene-sec-butyllithium adduct or initiatorsolution (f=4.85) to give 0.046 mmole CLi was added dropwise by syringeto a solution of 10.0 grams sieve-dried butadiene and 490.8 gramssieve-dried toluene in a dry, argon-purged quart polymerization bottleto a pale yellow end-point, indicating successful titration ofimpurities in the system. Promptly, 11.33 grams of adduct or initiatorsolution (2.25 mmoles CLi) were added to effect polymerization. A clearred solution was in evidence. The bottle was charged to a 30° C.rotating bath overnight. In the morning, the solution was pale orangeand slightly turbid. 16.3 grams of styrene monomer (distilled from Bu₂Mg) were added and allowed to react with rotation at 30° C. overnight.In the morning, an orange solution was found.

The majority of the solution was transferred under argon into 200 ml ofsieve-dried tetrahydrofuran which had been saturated with dry carbondioxide. Throughout the transfer, a vigorous carbon dioxide purge wasmaintained at the addition site by needle, with the polymer solutioninlet held below the liquid surface. Agitation by magnetic stirring barmixed the solution. Color loss at the addition site occurred instantlywith no evidence of unreacted lithium carbanion found.

The polymer was precipitated in excess methanol and dried under vacuum.Carboxyl content was determined to be 0.0356 mmole COOH/gram polymer oran average of 3.3 carboxyls per molecule, based on equation 2, withmmoles carboxyl substituted for mmoles OH.

In this polymer as initially prepared, each arm extending from theinitiator nucleus has a polybutadiene block then a polystyrene blockterminating in C-Li. Thus from the end of one arm to the end of anotherarm there is provided ##STR2## N being the nucleus from the initiator.

EXAMPLE 9

The following thermosetting polyester glass fiber compositions wasprepared:

    ______________________________________                                                           Parts by Weight                                            Ingredient           I      II     III  IV                                    ______________________________________                                        Polyester resin      210    210    210  210                                   (70% by wt polypropylene                                                      fumarate (acid no. of 20 and                                                  OH no. of 30) and 30% by wt.                                                  styrene)                                                                      10% by wt benzoquinone in styrene                                                                  1.8    .17    .17  .17                                   Styrene              10.5   50     50   50                                    Mixture of 70% by wt. of styrene                                                                   138    --     --   --                                    and 30% by wt. of polymethyl-                                                 methacrylate                                                                  MgO ("Maglite" D)    5.7    --     --   --                                    Zinc Stearate        18     18.4   18.4 18.4                                  CaCO.sub.3 ("Camel-Wite," Campbell                                                                 525    525    525  525                                   Grove Div. of H. M. Royal)                                                    Tertiary Butyl Perbenzoate                                                                         2.7    2.7    2.7  2.7                                   Mixture of 70% by wt. of styrene                                                                   --     140    --   --                                    and 30% by wt. of carboxylated                                                Bd-Sty, approx. 15% styrene, and                                              approx m.w. of 100,000, block                                                 copolymer,                                                                    ("Solprene" 312, Phillips Chem. Co.,                                          a Div. of Phillips Pet. Co., contains                                         stabilizer and stearic acid)                                                  Mixture of 70% by wt. of styrene and                                                               --     --     140  --                                    30% by wt. of Bd-Sty star block                                               copolymer of this invention*                                                  Mixture of 70% by wt. styrene and                                                                  --     --     --   140                                   30% by wt. of carboxy terminated                                              Bd-Sty star block copolymer of                                                this invention**                                                              Mixture of MgO in a plasticizer                                                                    --     17.6   17.6 17.6                                  Glass Mat            242    242    242  242                                   ______________________________________                                         *Bd-Sty, star block copolymer, 16% by wt. of styrene, --Mn = 93,200 based     on charge. Tg = -89.2° C. No active end groups, protonated.            **Carboxy terminated BdSty star block copolymer, 15.3% by wt. of styrene,     Tg = -88.6° C., --Mn = 91,500 based on charge, carboxyl content        0.0234 meq/gm polymer of 0.0608 meq/gm theo., 38.5% carboxyl converted,       2.11 carboxyl groups per molecule (average).                             

The above compositions contained from 10.5 to 11.3% of the low profileadditives.

The above ingredients except the glass were mixed together, and theresulting mixtures were forced into the glass mats at 80 lbs. pressurefor 3 minutes. Samples of the resulting glass impregnated mats were thencompression molded at about 300° F. (149° C.) and 1000 p.s.i. to formcured FRP samples which were then tested as shown in the Table below:

                  TABLE                                                           ______________________________________                                        Mold-                                                                         ings                                       Izod                               From          Flex     Flex                Impact                             Com-          Modulus  Strength                                                                             Tensile                                                                             Elonga-                                                                              Ft.                                posi- Shrink- PSI ×                                                                            PSI ×                                                                          PSI ×                                                                         tion   lb/in                              tion  age     10.sup.6 10.sup.4                                                                             10.sup.4                                                                            %      notch                              ______________________________________                                        I     .08     1.75     2.74   1.10  2.2     9.3                               II    .04     1.44     2.24   1.21  2.9    14.6                               III   .08     1.40     2.05   1.03  2.8    11.9                               IV    .08     1.39     1.94    .69  1.6    12.2                               ______________________________________                                    

From these results, it is demonstrated that the polymers of thisinvention are useful low shrink additives in FRPs.

We claim:
 1. The method which comprises polymerizing under inertconditions in a hydrocarbon solvent at a temperature of from about 0° to120° C., or from about 20° to 80° C., a polymerizable ethylenicallyunsaturated monomer having an activated unsaturated double bond with ahydrocarbon soluble, gel free and stable initiator in a minor amountsufficient to polymerize said monomer to obtain a polymer, saidinitiator being free of a solubilizing polymerizable comonomer andcomprising the adduct of RLi where R is selected from the groupconsisting of normal, secondary and tertiary alkyl and cycloalkylradicals of from 2 to 20 carbon atoms, or from 2 to 10 carbon atoms, anda diethylenically unsaturated aromatic compound selected from the groupconsisting of divinyl benzene and disopropenyl benzene and mixturesthereof, the mole ratio of RLi to said aromatic compound being about1:0.83, said adduct having an average of from about 4 to 9 C-Li sitesand a VPO Mn of from about 750 to 4,000 and said polymer having anaverage of from about 4 to 9 arms and having Li atoms on the ends ofsaid arms.
 2. The method according to claim 1 where RLi is secondarybutyllithium and said aromatic compound is divinyl benzene.
 3. Themethod according to claim 1 where said monomer comprises about 10 to 40%by weight of styrene and 90 to 50% by weight of butadiene-1,3.
 4. Themethod according to claim 3 where the butadiene-1,3 is substantiallypolymerized first.
 5. The method according to claim 2 where said monomercomprises about 10 to 40% by weight of styrene and 90 to 60% by weightof butadiene-1,3.
 6. The method according to claim 5 where thebutadiene-1,3 is substantially polymerized first.
 7. A rubbery starcopolymer having an average of from about 4 to 9 arms, having Li atomson the ends of the arms, having a Mn of from about 50,000 to 250,000,comprising from about 10 to 40% by weight of styrene and from 90 to 60%by weight of butadiene-1,3 and having a nucleus from an initiator (1)having a VPO Mn of from about 750 to 4,000, (2) having from 4 to 9 C-Lisites and (3) being the adduct of an aromatic compound selected from thegroup consisting of divinyl benzene and diisopropenyl benzene andmixtures thereof and RLi where R is from the group consisting of normal,secondary and tertiary alkyl and cycloalkyl radicals of from 2 to 20, orfrom 2 to 10, carbon atoms, the mole ratio of RLi to said aromaticcompound being about 1:0.83.
 8. A rubbery star copolymer according toclaim 7 which is a block copolymer and where the end portions of thearms comprise polystyrene blocks.
 9. A rubbery star copolymer accordingto claim 8 in which the said Li atoms have been replaced with terminalcarboxyl groups.